iptables dyndns etc..

any help please.....
Linksys 54gl PPOE- dlink modem-bridge mode.One PC NIC static IP - eth1.PC is share server, ports are forward in router and are open dyndns adress also,with certain emu sharing is ok.I need some IPTABLES script or rules etc.. in the following way I supose.1 udp port open, 1 tcp port open, internet port for surfing is open and host-dns throug in/out to my peer.All the rest, strictly closed ,21,22,23, all close ..
I hope I have managed to explain, and also I hope any solution or some skript,rule, etc for the above problem.